One‐Pot Synthesis of Cu‐Nanocluster‐Decorated Brookite TiO₂Quasi‐Nanocubes for Enhanced Activity and Selectivity of CO₂ Photoreduction to CH₄

Abstract

A new kind of metallic Cu‐loaded brookite TiO2 composite, in which Cu nanoclusters with a small size of 1–3 nm are decorated on brookite TiO2 quasi nanocube (BTN) surfaces (hereafter referred to as Cu‐BTN), is synthesized via a one‐pot hydrothermal process and then used as photocatalyst for CO2 reduction. It was found that the decoration of Cu nanoclusters on BTN surfaces can improve the activity and selectivity of CO2 photoreduction to CH4, and 1.5 % Cu‐BTN gives a maximum overall photocatalytic activity (150.9 μmol g−1 h−1) for CO/CH4 production, which is ≈11.4 and ≈3.3 times higher than those of pristine BTN (13.2 μmol g−1 h−1) and Ag‐BTN (45.2 μmol g−1 h−1). Moreover, the resultant Cu‐BTN products can promote the selective generation of CH4 as compared to CO due to the number of surface oxygen vacancies and the CO2/H2O adsorption behavior, which differs from that of the pristine BTN. The present results demonstrate that brookite TiO2 would be a potential effective photocatalyst for CO2 photoreduction, and that Cu nanoclusters can act as an inexpensive and efficient co‐catalyst alternative to the commonly used noble metals to improve the photoactivity and selectivity for CO2 reduction to CH4.

Atomic‐Level Reactive Sites for Semiconductor‐Based Photocatalytic CO2 Reduction

“…Moreover, following CO 2 − desorption from oxygen vacancies, the oxygen vacancy can be formed again under light irradiation. The introduction of Cu clusters can improve the selectivity of CH 4 . The synergistic effect of oxygen vacancy and Cu has been studied .…”

“…The introduction of Cu clusters can improve the selectivity of CH 4 . [34] The synergistic effect of oxygen vacancy and Cu has been studied. [69] Under light irradiation, CO 2 molecule can form Cu + -CO and it is converted to www.advancedsciencenews.com CO according to the DRIFTS.…”

“…However, there remain three obstacles that limit the photocatalytic efficiency in terms of the redox reaction. First is the difficulty for gaseous CO 2 to be absorbed by solid photocatalysts . This heterogeneous catalysis makes absorption and diffusion of reactant on the surface of photocatalysts complex.…”

“…First is the difficulty for gaseous CO 2 to be absorbed by solid photocatalysts. [32][33][34][35] This heterogeneous catalysis makes absorption and diffusion of reactant on the surface of photocatalysts complex. Second, CO 2 molecules are highly thermodynamically stable.…”

“…Atomic‐level reactive sites can be introduced into photocatalysts via a range of strategies such as: introducing vacancies in the crystal lattice, doping single heterogeneous atoms, anchoring functional groups and loading metal complexes on the surface, and fabricating FLPs . With advances in characterization technologies and synthesis methods, researchers can design materials from atomic level to reveal fundamental photocatalytic CO 2 reduction from spatial‐and‐time perspectives using, for, e.g., high resolution transmission electron microscope (HRTEM), scanning transmission electron microscopy (STEM), and in situ technologies.…”